Suppressing Chemical and Galvanic Corrosion in Anode‐Free Lithium Metal Batteries Through Electrolyte Design

Abstract

The advancement of anode‐free lithium metal batteries (AFLMBs) is greatly appreciated due to their exceptional energy density. Despite considerable efforts to enhance the cycling performance of AFLMBs, the understanding of lithium corrosion, which leads to substantial capacity loss during the open circuit voltage (OCV), regardless of electrolyte chemistry, remains limited. In particular, the connection between electrolytes and lithium corrosion performance lacks clear understanding, and the impact of solid‐electrolyte interface (SEI) composition on resistance against lithium corrosion remains elusive. This study explores, for the first time, the effects of salt concentration and solvents on the lithium corrosion behavior in AFLMBs, utilizing the lithium bis(fluorosulfonyl)imide (LiFSI)‐1,2 dimethoxyethane (DME)‐1,3 dioxolane (DOL) electrolyte system. The findings reveal that increasing salt concentration leads to the suppression of chemical corrosion but exacerbation of galvanic corrosion. The key to effectively suppressing both chemical and galvanic corrosion lies in promoting the coordination of less‐soluble particles and polymers within the SEI. This conclusion is further validated by a two‐step electrolyte modification measurement. As a result, a new electrolyte formula, 0.5  M LiFSI‐0.5  M LiBF ₂(C ₂O ₄)‐0.5  M LiNO ₃(DME/fluoroethylene carbonate or FEC), is prepared and shown to have improved resistance to both chemical and galvanic corrosion, and the Coulombic efficiency loss from chemical corrosion is reduced to 0.13%.